[43] CHAPTER III 



PRELIMINARY REMARKS ON IMMUNITY IN THE 

 ANIMAL KINGDOM 



Examples of natural immunity among the Invertebrates.— Immunity against micro- 

 organisms and insusceptibility to microbial poisons are two distinct properties. — 

 The refractory organism does not eliminate micro-organisms by the excretory 

 channels. — It destroys them by a process of resorption. — The fate of foreign 

 bodies in the organism. — The resorption of cells. — Intracellular digestion. — 

 This digestion eflfected by the aid of soluble ferments.— Digestion in Planarians 

 and Actinians. — Actino-diastase.- Transition from intracellular digestion to 

 digestion by secreted juices. — Digestion in the higher animals.— Enterokynase 

 and the part it plays in digestion.— The psychical and nervous elements 

 in digestion. — Adaptation of the pancreatic secretion to the kind of food. — 

 Excretion of pepsin in the blood and in the urine. 



As shown in the two preceding chapters unicellular organisms 

 and plants afford evidence of numerous phenomena of immunity. 

 Alongside natural immunity we find in them undoubted evidence of 

 an adaptation to the presence of morbific agents, evidence which 

 warrants us in inferring that cases of acquired immunity are frequent. 

 This being the case it is quite natural that the animal kingdom should 

 be no exception to the general rule. Indeed, immunity against patho- 

 genic agents is widely distributed in animals, and we continually see 

 manifestations of natural immunity not only against parasites and 

 their toxins, but against poisons in general. Just as frequently we 

 find cases of acquired immunity against these morbific agents. 



As yet we know but little concerning the phenomena of immunity 

 in the lower animals belonging to the great group of the Invertebrata. 

 But it may be affirmed with certainty that these also are often 

 endowed with a natuml immunity against micro-organisms and 

 bacterial toxins. As an example I may cite the case of the large 

 white larvae of the Rhinoceros beetle {Oryctes nasicornis) frequently 

 met with in tanner's bark. Very susceptible to the cholera vibrio— 

 y^jj^ of a culture^ of this organism being sufficient to set up a fatal 



^ [Probably a surface growth on a sloped agar tube (Transl.).] 



